fix: switch GMW AI source from omniroute to 9router (model alias revert)

- Switch AI_LLM_BASE_URL from omniroute.imrnes.team to 9router.asepharyana.my.id
- Keep AI_LLM_MODEL as 'text' (9router uses alias-based routing, not bare names)
- Update .env.example comments to document 9router
- Per user: multimodal stays 'multimodal' alias

API verified: curl to 9router/v1/chat/completions with model 'text'
returns HTTP 200 (OpenAI-compatible format)

services/discord-gateway/src/shared/config/index.ts

@@ -150,7 +150,7 @@ export const configSchema = z
       .string()
       .url()
       .default("https://9router.asepharyana.my.id/v1"),
-    AI_LLM_MODEL: z.string().default("claude-opus-5"),
+    AI_LLM_MODEL: z.string().default("text"),
     // Vision uses the SAME router/base URL as text moderation
     // (AI_LLM_BASE_URL) but a different model alias. The dedicated NVIDIA
     // multimodal endpoint was removed.